1. Field of the Invention
This invention relates to high resiliency polyurethane foam surfactants. More specifically, this invention relates to novel surfactants made from polydialkylsiloxanepolyoxyalkylene copolymers which have secondary or tertiary hydroxy terminated polyoxylalkylene pendants on the copolymer. These surfactants have particular advantage in obtaining good breathability in high resiliency polyurethane foam with higher than normal amounts of solid polymer.
2. Prior Art
High resiliency polyurethane foams are produced by the reaction of high molecular weight polyols, which polyols have greater than 40% of primary hydroxyl capping, with organic isocyanates and water. High resiliency polyurethane foams are distinguishable, in part, from conventional hot cure polyurethane foams by the use of such a high percentage of primary hydroxyl groups as well as by the fact that high resiliency polyurethane foams require little or no oven curing and thus are often referred to as cold cure foams. Such foams are extremely desirable for cushioning applications because of their excellent physical properties, e.g., very high foam resiliency, open celled structure, low flex fatigue, i.e., long life, and high SAC factors, i.e., load bearing properties.
Because of the high reactivity of high resiliency foam ingredients and their rapid buildup of gel strength, sometimes the foam can be obtained without a cell stabilizer. However, such foams typically have very irregular, coarse cell structure as particularly evidenced by surface voids. A variety of attempts have been made to solve this problem through the use of stabilizers consisting of substituted polydimethyl- or polyphenylmethylsiloxanes.
One group of stabilizers, described in U.S. Pat. Nos. 3,741,917 to Morehouse et al and 4,031,044 to Joslyn et al., is based on polydimethylsiloxanepolyoxyalkylene copolymers. The polyoxyalkylene pendant groups on the stabilizers in these patents, however, are always hydrocarbon capped.
Other polysiloxanes bearing pendant groups have also been claimed as stabilizers for high resiliency urethane foam. In general they are copolymers consisting of a polydimethylsiloxan to which are attached organic pendant groups that include: methyl groups (U.S. Pat. No. 2,901,445); cyanoalkyl groups (U.S. Pat. No. 3,905,924); phenylethyl groups (U.S. Pat. No. 3,839,384); alkyl groups (U.S. Pat. No. 4,306,035); trimethylsiloxy groups (U.S. Pat. No. 3,884,847); sulfolanyloxyalkyl groups (U.S. Pat. No. 4,110,272); morpholinoalkoxyalkyl groups (U.S. Pat. No. 4,067,828), and the tertiary hydroxyalkyl group (U.S. Pat. No. 4,039,490). None of these patents suggest hydroxy terminated polyoxyalkylene pendant groups attached to the siloxane chain.
Recent U.S. Pat. No. 4,478,957 to Klietsch et al does describe polysiloxanepolyoxyalkylene copolymers wherein the polyoxyalkyalkylene portions of the copolymer are either totally hydroxy terminated or totally alkyl, carboxy, or alkylaryl capped.
All of the above mentioned stabilizers have been designed for high resiliency polyurethane foam containing low levels of reinforcing grafted copolymer rather than those containing high concentrations of these materials. This distinction is important for reasons discussed below.
Grafted copolymer polyols are typically prepared by polymerizing one or more ethylenically unsaturated monomers, for example styrene and acrylonitrile, in a polyether polyol, or by reacting diisocyanates with polyamines or hydrazines in a polyether polyol. Typically, the grafted copolymer polyols for current polyurethane formulations contain about 20 percent solids in the polyol. This is normally formulated as about 50 percent of the final grafted copolymer content, thus bringing the actual solids content to about 10 percent.
Recently, however, it has become desirable to manufacture high resiliency foam with increased firmness. Increased firmness is desirable so that thinner or lower density foam sections can be manufactured with load bearing properties equal to sections currently being made, or for the manufacture of sections with greater firmness where higher load bearing foam is desired. Such improved foams are especially desirable in the automotive seat market where reduced size and weight are important considerations in the design of smaller automobiles. One important method of achieving greater foam firmness is to increase the concentration of solids used in the urethane formulation.
Most recently, blends of conventional flexible polyurethane foam surfactants and high resiliency polyurethane foam surfactants (U.S. Pat. Nos. 4,309,508 and 4,477,601) have been taught as a method of increasing the concentration of these solids in the total polyol mixture. The small amounts of a conventional surfactant required presents considerable difficulties as minor errors in preparing these stabilizers can have significant, adverse effects on the performance characteristics of foam stability or foam breathability. Also, as in those systems for stabilizing low levels of grafted copolymer solids, hydroxy groups are not present as the capping group in the pendant chain of these copolymers.
Of further concern in selecting a stabilizer is the breathability or open celled character of foam. Greater breathability, i.e., more open celled character, of the foam is desirable because it provides a greater processing latitude. A narrow processing latitude forces the foamer to adhere to very close tolerances in metering out the foaming ingredients which can not always be accomplished. Further, greater breathability provides foam that is easier to crush, thus avoiding splits that might occur during crushing. This characteristic is particularly desirable in foamed arts that incorporate wire inserts which are difficult to crush.
Recently, U.S. patent application Ser. No. 880,295 filed June 30, 1986 disclosed mixed functional pendant silicone surfactants for stabilization of high solids, high resilienc polyurethane foam. The mixed monomer polyethers of that patent application are prepared in the manner customary to the art by coreacting the desired alkylene oxides with the starting alkoxide. This allows for the kinetic determination of terminal group rather than the addition controlled method claimed in this patent. No mention is made of controlling the foam openness by changing the nature of the alcohol terminal group.
This invention provides stabilizers that continue to provide foam stability for the desired higher levels of grafted copolymer solids in high resiliency molded polyurethane foam while also providing high breathability foams, i.e. foams with a much more open celled character. A method is provided for preparing these stabilizers. A method is further provided for meeting the stability and breathability requirements of particular firm foam formulations over a wide range of reinforcing grafted copolymer concentrations.